Our study is directed towards the identification of the molecules in the membrane involved in the interaction with sugar during absorption. In addition we are interested in the mechanisms of the carrier function. Several systems are used for the study of transport, the erythrocyte membrane the intestinal cell preparation using isolated cells and vesicles and the kidney vesicle preparation. In previous work we have been able to prepare several photoaffiniy probes capable of interaction with the carrier. This work is continued. We are presently in the process of preparing these probes in radioactive form. This approach can be used for the understanding of the transport of nonionic nutrients in mamalian cells in general.